Mission Expansion and Farm Rewrite

Added a couple of functions to make creating missions easier.  Commands to have the NPC giving the mission join your party at the start and a separate one to leave the party (so at the end of the story line you can loose a long time companion).  New mission goal to take the NPC to a certain type of building/tile.  Added two missions to the "humanitarian" mission path.  

For farms, I connected fences for adjacent farm fields to limit fence spawn.  A 1/10 chance to spawn a farm house that is per-fortified/used.  The intention is to have an NPC/NPCs spawn with it once NPCs are fully integrated to regular game play.